This invention relates to a method for flaring an end of a plastic pipe liner installed inside a pipe.
It is known to line metal pipes with plastic liners to rehabilitate them and/or to provide corrosion or chemical resistance. There are many different methods of lining pipe known in the art. Canadian Patent 1,241,262 (Du Pont Canada Inc.) discloses a method and apparatus for lining pipe which involves taking a liner of a larger O.D. than the I.D. of the pipe to be lined, reducing the diameter of the liner with driven rollers and pulling the liner into the pipe. The pulling force is then released and the liner is allowed to expand and fit tightly against the wall of the pipe.
It is known to weld plastic flanges to the ends of the liner after installation so that liner segments may be joined together. However, it is difficult to do this after the liner has been inserted into a pipe.
U.S. Pat. Nos. 4,383,966 (Svetlik) and 4,156,710 (Caroll et al.) both teach the idea of flaring thermoplastic pipe ends to form flanges thereon. However, neither of these patents teach a method of carrying this out on a thermoplastic liner installed inside a pipe.
U.S. Pat. No. 3,341,894 (Flaming) teaches the idea of flaring the end of a liner installed inside a pipe by using a heated plug. It has been found that using a single plug of the design disclosed in this patent causes the end of the liner to curl under itself.
U.S. Pat. No. 4,525,319 (Kaspe) discloses a method and apparatus for forming a flange on a thermoplastic pipe inside a sleeve. The invention employs only a single head to move the end of the liner through an obtuse angle to form a flange. This head may cause the liner to buckle or it may cause the liner to curl under itself, which in either case will create an unsatisfactory flange.
It is desirable to flare the end of the liner after it has been installed in a pipe to form a flared end while inhibiting buckling or curling of the liner under itself.